187 lines
5.9 KiB
Markdown
187 lines
5.9 KiB
Markdown
# 安装 kubedns 插件
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官方的 yaml 文件目录：`kubernetes/cluster/addons/dns`。
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该插件直接使用 kubernetes 部署，官方的配置文件中包含以下镜像：
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```ini
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gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.1
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gcr.io/google_containers/k8s-dns-kube-dns-amd64:1.14.1
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gcr.io/google_containers/k8s-dns-sidecar-amd64:1.14.1
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```
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我 clone 了上述镜像，上传到我的私有镜像仓库：
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```ini
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harbor-001.jimmysong.io/library/k8s-dns-dnsmasq-nanny-amd64:1.14.1
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harbor-001.jimmysong.io/library/k8s-dns-kube-dns-amd64:1.14.1
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harbor-001.jimmysong.io/library/k8s-dns-sidecar-amd64:1.14.1
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```
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以下 yaml 配置文件中使用的是私有镜像仓库中的镜像。
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```ini
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kubedns-cm.yaml
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kubedns-sa.yaml
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kubedns-controller.yaml
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kubedns-svc.yaml
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```
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已经修改好的 yaml 文件见：[../manifests/kubedns](https://github.com/rootsongjc/kubernetes-handbook/blob/master/manifests/kubedns)
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## 系统预定义的 RoleBinding
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预定义的 RoleBinding `system:kube-dns` 将 kube-system 命名空间的 `kube-dns` ServiceAccount 与 `system:kube-dns` Role 绑定， 该 Role 具有访问 kube-apiserver DNS 相关 API 的权限；
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```bash
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$ kubectl get clusterrolebindings system:kube-dns -o yaml
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apiVersion: rbac.authorization.k8s.io/v1beta1
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kind: ClusterRoleBinding
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metadata:
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annotations:
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rbac.authorization.kubernetes.io/autoupdate: "true"
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creationTimestamp: 2017-04-11T11:20:42Z
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labels:
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kubernetes.io/bootstrapping: rbac-defaults
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name: system:kube-dns
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resourceVersion: "58"
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selfLink: /apis/rbac.authorization.k8s.io/v1beta1/clusterrolebindingssystem%3Akube-dns
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uid: e61f4d92-1ea8-11e7-8cd7-f4e9d49f8ed0
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roleRef:
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apiGroup: rbac.authorization.k8s.io
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kind: ClusterRole
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name: system:kube-dns
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subjects:
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- kind: ServiceAccount
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name: kube-dns
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namespace: kube-system
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```
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`kubedns-controller.yaml` 中定义的 Pods 时使用了 `kubedns-sa.yaml` 文件定义的 `kube-dns` ServiceAccount，所以具有访问 kube-apiserver DNS 相关 API 的权限。
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## 配置 kube-dns ServiceAccount
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无需修改。
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## 配置 `kube-dns` 服务
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``` bash
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$ diff kubedns-svc.yaml.base kubedns-svc.yaml
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30c30
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< clusterIP: __PILLAR__DNS__SERVER__
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---
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> clusterIP: 10.254.0.2
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```
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+ spec.clusterIP = 10.254.0.2，即明确指定了 kube-dns Service IP，这个 IP 需要和 kubelet 的 `--cluster-dns` 参数值一致；
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## 配置 `kube-dns` Deployment
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``` bash
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$ diff kubedns-controller.yaml.base kubedns-controller.yaml
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58c58
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< image: gcr.io/google_containers/k8s-dns-kube-dns-amd64:1.14.1
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---
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> image: harbor-001.jimmysong.io/library/k8s-dns-kube-dns-amd64:v1.14.1
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88c88
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< - --domain=__PILLAR__DNS__DOMAIN__.
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---
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> - --domain=cluster.local.
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92c92
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< __PILLAR__FEDERATIONS__DOMAIN__MAP__
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---
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> #__PILLAR__FEDERATIONS__DOMAIN__MAP__
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110c110
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< image: gcr.io/google_containers/k8s-dns-dnsmasq-nanny-amd64:1.14.1
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---
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> image: harbor-001.jimmysong.io/library/k8s-dns-dnsmasq-nanny-amd64:v1.14.1
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129c129
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< - --server=/__PILLAR__DNS__DOMAIN__/127.0.0.1#10053
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---
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> - --server=/cluster.local./127.0.0.1#10053
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148c148
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< image: gcr.io/google_containers/k8s-dns-sidecar-amd64:1.14.1
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---
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> image: harbor-001.jimmysong.io/library/k8s-dns-sidecar-amd64:v1.14.1
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161,162c161,162
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< - --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.__PILLAR__DNS__DOMAIN__,5,A
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< - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.__PILLAR__DNS__DOMAIN__,5,A
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---
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> - --probe=kubedns,127.0.0.1:10053,kubernetes.default.svc.cluster.local.,5,A
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> - --probe=dnsmasq,127.0.0.1:53,kubernetes.default.svc.cluster.local.,5,A
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```
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+ 使用系统已经做了 RoleBinding 的 `kube-dns` ServiceAccount，该账户具有访问 kube-apiserver DNS 相关 API 的权限；
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## 执行所有定义文件
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``` bash
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$ pwd
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/root/kubedns
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$ ls *.yaml
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kubedns-cm.yaml kubedns-controller.yaml kubedns-sa.yaml kubedns-svc.yaml
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$ kubectl create -f .
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```
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## 检查 kubedns 功能
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新建一个 Deployment
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``` bash
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$ cat >> my-nginx.yaml << EOF
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apiVersion: extensions/v1beta1
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kind: Deployment
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metadata:
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name: my-nginx
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spec:
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replicas: 2
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template:
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metadata:
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labels:
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run: my-nginx
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spec:
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containers:
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- name: my-nginx
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image: harbor-001.jimmysong.io/library/nginx:1.9
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ports:
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- containerPort: 80
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EOF
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$ kubectl create -f my-nginx.yaml
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```
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Export 该 Deployment, 生成 `my-nginx` 服务
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``` bash
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$ kubectl expose deploy my-nginx
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$ kubectl get services --all-namespaces |grep my-nginx
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default my-nginx 10.254.179.239 <none> 80/TCP 42m
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```
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创建另一个 Pod，查看 `/etc/resolv.conf` 是否包含 `kubelet` 配置的 `--cluster-dns` 和 `--cluster-domain`，是否能够将服务 `my-nginx` 解析到 Cluster IP `10.254.179.239`。
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``` bash
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$ kubectl create -f nginx-pod.yaml
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$ kubectl exec nginx -i -t -- /bin/bash
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root@nginx:/# cat /etc/resolv.conf
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nameserver 10.254.0.2
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search default.svc.cluster.local. svc.cluster.local. cluster.local. jimmysong.io
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options ndots:5
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root@nginx:/# ping my-nginx
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PING my-nginx.default.svc.cluster.local (10.254.179.239): 56 data bytes
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76 bytes from 119.147.223.109: Destination Net Unreachable
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^C--- my-nginx.default.svc.cluster.local ping statistics ---
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root@nginx:/# ping kubernetes
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PING kubernetes.default.svc.cluster.local (10.254.0.1): 56 data bytes
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^C--- kubernetes.default.svc.cluster.local ping statistics ---
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11 packets transmitted, 0 packets received, 100% packet loss
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root@nginx:/# ping kube-dns.kube-system.svc.cluster.local
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PING kube-dns.kube-system.svc.cluster.local (10.254.0.2): 56 data bytes
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^C--- kube-dns.kube-system.svc.cluster.local ping statistics ---
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6 packets transmitted, 0 packets received, 100% packet loss
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从结果来看，service 名称可以正常解析。
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```
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**注意**：直接 ping ClusterIP 是 ping 不通的，ClusterIP 是根据 **IPtables** 路由到服务的 endpoint 上，只有结合 ClusterIP 加端口才能访问到对应的服务。
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